A practical learning and memory screening test in rats using a modified Biel water maze - A multi-site validation

Developmental and adult neurotoxicity testing is an integral part of safety assessment guidelines. A key endpoint, typically performed in rodents, is the evaluation of learning and memory (L&M). Historically, a variety of equipment and testing paradigms have been developed and used across the industry. In recent years, regulatory guidance documents have become more prescriptive and stipulate specific types of tests to be used at different ages. The most common L&M tests for developmental neurotoxicity are performed using water mazes. Navigational L&M can be split into two principal types where animals use external visual cues from the surrounding environment for allocentric navigation (tested in a Morris water maze), and internal cues for egocentric navigation (tested in multiple T-mazes, such as the Biel or Cincinnati water maze, when performed in complete darkness [under infrared lighting]). With increasing degrees of light and the consequent visibility of distal cues, there is a shift towards a combination of egocentric and allocentric navigation. This paper provides methodological details of a practical screening test for L&M for juvenile, young-adult and mature rats using a modified Biel water maze under red light, which has been validated using a positive control across multiple Charles River facilities. Other available water mazes, such as Cincinnati and Morris water mazes have limited proficiency in weanling (PND 21-22) rodents. This manuscript illustrates that the modified Biel water maze can be used to screen for deficits in learning and memory in juvenile (weanling) rats, as well as at older life stages, in compliance with published regulatory guidelines for safety assessment studies.